Fluid pressure actuating system



Jan. 9, 1945.

w. F. BoLDT Filed Jan. 7, 1943 3 Sheets-Sheet l IHM fun Jan. 9, 1945. w. F. BOLDT 2,365,696

FLUIDl PRESSURE ACTUTING SYSTEM Filed Jan. 7, 1943 :s sheets-sheet z i F163 I 4 v e FIGZ.

, INVENTOR W.F.BOLDT ATTORNEY FLUID PRESSURE ACTATING SYSTEM @()GQQO 63 INVENT'R w. F. BOL DT 4 gf/W ATTORNEY Patented Jan. 9, 1945 FLUID PRESSURE ACTUATING SYSTEM Werim- F. Boldt, clayton, Mo., assigner to Wagner Electric Corporation, St. Louis. Mo., a

corporation o! Delaware Application January 7, 1943, Serial No. 471,551

(Cl. 18S-152) v20 Claims.

My invention relates to actuating systems and more particularly to a hydraulic actuating system' which may, if desired, have an air pressure V system associated therewith.

One of the objects of my invention is to produce a hydraulic actuating system for a plurality of devices which can be controlled by separately operated pressure producing devices.

Another object of my invention is to combine a selector control valve with one of said pressure producing devices and to provide a single manual member for operating the` device and valve in a desired sequence or only the device.

Another and more specific object of my invention is to produce an improved hydraulic brake actuating system for a vehicle. which can be so controlled that certain brakes `can be operated to assist in steering the vehicle.

Other objects of my invention will become apparent from the following description taken in connection with the accompanying drawings in which Figure 1 is a schematic view of a hydraulic brake actuating system for a vehicle having myl invention embodied therein; Figure 2 is a front view of the combined pressure producing device and selector valve; Figure 3 is a longitudinal sectional view through said combined device and .valve; Figures 4 and 5 are sectional views taken on the lines 4--4 and 5 5, respectively, of Figure 3; and Figure 6 is a schematic view of another brake actuating system in which my invention is embodied.

Referring to the drawings in detail, my invention is shown embodied in a hydraulic actuating system for the brakes of a motor vehicle but such is by way of example only as it can be embodied in any iiuid system where the results obtained are desirable. In Figure 1 the dirigible front wheels I and 2 of'said vehicle, the right rear driving wheels 3, and the left rear driving wheels 4 are schematically shown. All of these wheels are provided with brake assemblies 5 which are I actuated by-iiuid motors 5'. 'I'he uid medium employed to control the brakes is a liquid and the source ofl pressure comprises the well-known master cylinder device 6 operated by a pedal 1.

The outlet of the master cylinder is connected by a conduit 8 with my novel combined master cylinder and selector valve mechanism generally indicated by the numeral 3. A conduit III leads from this combined mechanism to the iluid motors on the two front wheels to operate the brake assemblies thereof. There is also a conduit II which leads to the iluld motors of the brakes leads to the fluid motors of the brakes on the left rear wheels. A conduit 8 is associated with the mechanism to connect one port thereof to later.'

another port, the reason therefor to be described As shown in detail in Figures 2, 3, 4, and 5, the combined master cylinder and control valve mechanism 9 comprises a main body member I3 to which is tltted a casing member I4 and a bottom plate member I5. The body member and plate member are so formed as to provide a chamber I6 therebetween to which is connected conduit 8 for conducting iluid under pressure from either of the two master cylinders. This chamber I6 has three outlet passa-ges Ill, I8, and I9 (see Figure 5) arranged 120 degrees apart in the body member I3.` The outlet passage I1 is connected with conduit l0 leading to the front brakes and passages IB and I9 are connected to conduits I2 and II, respectively, leading to the rear brakes. Passages I'I, I8, and I9 have shutoff valves 20, 2|, and 22, respectively .associated therewith.

As best shown in Figure 3, each of these valves comprises a plunger 23 slidably mounted in the bottom plate I5. The plungers are spaced 180 degrees apart with their axes parallel with the vertical axis of the body member. A spring 24 biases each plunger toward seated or closed position. The valves are controlled by a rotatable disc cam 25 mounted in the body member I3 with its peripheral portion being received in cross notches 26 in the valve plungers so that the cam surfaces which are formed as flanges on the disc may cause the plungers to be reciprocated. As best shown in Figures 3 and 5, the disc cam has a short high portion 2'I for cooperation with the plunger ofv valve 20 and a long high portion 28 extending over approximately degrees for cooperation with the plungers of valves 2| and 22. Between the high portions 21 and 28 are low portions 29 and 30.

When the ydisc is in its normally inoperative position, as shown in the figures, the high portions thereof will be so positioned that all the plungers of the valves will beheld in unseated position. If the disc should be turned in a clockwise direction, as viewed in Figuref, the plungers of valves 20 and 2| will be moved to valve closed position by the action of springs 24 due -to the fact that the low portions 29 and 30 of the cam are moved into-the slots of the plungers. It the disc should be moved in a counter-clockwise direction, then the plungers of valves 20 and on the right rear wheels and a conduit I2 which '66 22 will be moved to closed positions by their f ysprings due to the fact that the low portions 29 -between s aid disc and the bottom plate.

and 30 are moved into the slots of said plungers.

The disc is provided with a stem 3| which extends through the body member I3 into casing I4 and in order to seal this stem, there is provided a sealing washer 32 which is compressed by a spring 33 acting on the disc and positioned The inner end of the stem has a rectangular crosssection and is received in a rectangular opening in a member 34. This member is journaled for both rotative and axial movement. The end of member 34 adjacent the body member I3 is formed with a cam surface 35 for cooperation with a complementary cam surface 36 carried by the body member I3 (see Figure 3). The member 34 is adapted to be turned by a lever or handle 31 which is pivoted to said member by pins 38 (Figure 4), said handle projecting through a slot 39 in the wall of the casing member I4 in order to be accessible from the exterior. A spring 40 positioned in the casing member acts on member 34 to hold the cooperating cam surfaces 35 and 36 in engagement with each other,

.and also to bias the handle into engagement with the lower edge of the slot through which it extends.

When the handle is in the central part of the slot, cam surfaces 35 and 36 on member 34 `and body member I3 will be in complementary engagement and disc 25 will have the position shown in Figure wherein all the shut-off valves are in open position. If the handle should be moved to the right, as viewed in Figure 2,' member 34 will be rotated and also disc 25. This will position the disc so that valves 20 and 2l become closed, valve 22 remaining open, The cam surfaces 35 and 36 will cause member 34 to move upwardly and compress spring 40. If, after moving the handle to the right, the operator should release said handle, spring 40 acting through cam surfaces 35 and 36 will return the handle to its central position. The disc now returns to the position wherein all the shut-oil valves will again be held open. If the lever should be turned tothe left, as Viewed in Figure 2, the disc will be so rotated that the shutoff valves 20 and 22 will be permitted to become closed, shut-off valve 2l remaining open. Spring 4U will again be compressed by member 34 being moved upwardly by the action of cam surfaces 35 and 36. When the operators hand is released from the handle, the handle will snap back to its central position under the action of spring 46.

A. bleeder valve 4I is associated with chamber I6 so that air can be removed from the system when filling it with liquid or at any other time.

The casing member I 4 contains a second master cylinder device, cylinder` 42 of which communicates with conduit 8 leading from the master cylinder device 6, the connection being made by a closure plug 43 for the cylinder. The upper end of the cylinder is provided with an outlet 44 which is connected to the previously referred to conduit 8' connected to chamber I6. Within the cylinder is a piston 45 having a sealing cup 46. The rear end of this piston is formed to receive the upper end of the rotatable and axially movable member 34 previously referred to in order to form a bearing for this member and also a connection between it and the piston. The piston is normally held in retracted position by a spring 41 wherein it abuts member 34. The inlet port in plug 43 has associated therewith a valve element 48 carried by piston 45. This valve element is so mounted on the piston that when the piston is ,in its retracted position, the valve element will be unseated .but when the piston is initially moved forwardly, the valve element will assume a seated position. The piston is permitted to have relative movement with the valve element after the valve element is seated, A spring 49 is interposed between the valve element and the piston and normally holds the valve element biased against a cap 50 through which it projects. When the piston moves relatively to the valve element after closing it, spring 49 will be compressed. A bleeder valve 5I is provided for the chamber of the cylinder ahead of the piston in order that air can be removed when the system is being filled with liquid or at any other time. i

Whenever handle 31 is swung in either direction from its central position, member 34 will be moved axially as already noted. This axial movement will cause movement of piston 45 and closing of valve 48 to prevent fluid from being forced out into conduit 8. The valve element 48 will be closed at approximately the same time as the controlled shut-off valves are permitted to become closed, said valve closings occurring when the lever is moved only a part of the distance toward either end of slot 39. As handle 31 continues to be moved to an end of the slot, the piston 45 will also continue to be moved and will develop hydraulic pressure which will be transmitted through conduit 8', into chamber I6, and then either conduit I I or I2 depending upon which direction the handle is moved to leave either shutoff valve 2| or 22 open. Thus the driving wheel brakes will be selectively actuated solely bythe manipulation of handle 31. Therefore, itis not necessary to operate the master cylinder device 6 in order to employ the brakes to assist in steering.

It is also to be noted that handle 31 can be employed to actuate piston 45 and cause hydraulic pressure to be developed to operate all the brakes. This is accomplished by pulling down on handle 31. The handle will then fulcrum on the lower edge of slot 39 and member 34 will be moved axially without any rotation. This axial movement causes closing of valve 48 and the development of pressure by piston 45. The central part of the lower edge of the slot is rounded as indicated at 52 in order to permit free rocking of the handle and also easy sliding of the handle on the edge of the slot as member 34 is moved axially. The handle is also provided with cut away portions 53 and .54 in order that it may be freely rocked on its trunnions.

It is to be noted that in the event the limited extent of movement of piston 45 is insuiiicient to develop the desired pressure, the master cylinder device 6 can always be operated at any time to supplement this pressure as valve 48 will become unseated whenever the pressure developed by the master cylinder 6 is greater than that being developed by piston45.

From the foregoing description of the system, it is seen that all the brakes may be applied by operation of the master cylinder 6 and the driving wheel brakes on opposite sides of the vehicle may be selectively applied solely by the manipulation of the single handle7 or lever. This is accomplished by merely moving the handle in one dia rotative movement of handle 31 to either end of slot 39 will cause closing of valve 48 and the trapping of fluid under pressure in all the fluid motors. To hold the brakes applied itis thus not necessary to continue to operate the master cylinderv 6 as it can be released without releasing the brakes as long as handle 31 is held at either end of the slot. Whenever the hand of the operator is removed from the handle, the parts will automatically assume their, inoperative positions shown in Figure 3 due to the action of spring 40 and the arrangement of cam surfaces 35 and 36. A latch 31 (Figure 2) is provided to hold the handle at one end of the slot if such' should ever be desirable. This permits the brakes to be maintained applied, if previously` applied b`y the master cylinder 6, and allows the operator to leave the vehicle parked with the brakes applied.

, Referring now to Figure 6, I have shown a braking system similar to that of Figure 1 but having embodied therein a power means for developing the fluid pressure which operates the brakes, said power means being controllable by either the foot-operated master cylinder 6 or the mastercylinder of the combined master cylinder and selector valve mechanism 9. In the schematic view the driving members 3' and 4' on opposite sides of the vehicle are shown as tracks instead of wheels. The vehicle is provided with the dirigible wheels l and 2 and all the parts of the braking system which are the same as those of Figure 1 are indicated by the same reference characters, said parts comprising the master cylinder 6, the combined master cylinder and selector valve mechanism 9, and conduits 6, I0, Il, and I2. The conduit 8' of the system of Figure l is eliminated and the port Mis connectedrbyf'a conduit 55 with a vacuum-operated hydraulic pressure developing means generally indicated by the reference character 56. vThis means has a master cylinder 51, the outlet of which is connected by a conduit 58 to chamber I6 at the bottom of the combined master cylinder and selector valve mechanism 9. The master cylinder 51 is operated by a vacuum power cylinder 59 which is connected by conduits 6U and 6| to a source of vacuum such as the manifold 6'2 of engine 63. Interposed between conduits 60 and 6I is a control valve 64 comprising an inlet valve element 65 and an exhaust valve element 66, both of which are controlled by a floating lever 61.

The means for actuating the control valve comprises a piston 68 reciprocable in a cylinder 69. This piston is connected into conduit 55 in order to be operated by fluid pressure developed by the master cylinder 6 or the master cylinder in the combined master cylinder and selector valve mechanism 9. v

The power operated hydraulic pressure produc ing means described is ofeknown construction. When associated with the braking system in the manner shown, the hydraulic pressure developed by either the master cylinderl 6 or the master cylinder in the combined master cylinder and selector valve mechanism 9 will cause the piston of the master cylinder 51 to be operated and to begin to` develop pressure to actuate the brakes. Simultaneously therewith the control valve 64 will be so operated that the exhaust valve will be closed and the inlet valve opened 4so that the vacuum power cylinder 59 will be operated. When this power cylinder is operated, it will act in conjunction with the hydraulic developed pressure to actuate the master cylinder 51. Thus it is seen that this master cylinder 51 is operated by both hydraulic pressure and a power means in thc form of a vacuum-operated power cylinder. The advantage of this is to boost the hydraulic pressure which is manually developed by either the master cylinder 6 or the master cylinder in the combined master cylirfder and selector valve mechanism 9.

If the master cylinder 6 should be operated by the foot pedal, all the brakes will be applied since all the shut-ofi valves are open. If handle 31 should he turned in either direction, a brake of a driving member will be selected and applied, If handle' 31 should be rocked when in its central position, all the brakes will be applied. Thus it is seen that the system is operated in thcsame manner as the system in Figure 1. The only difference is that there 'is means provided for boosting the manually-developed hydraulic pressure in order that the brakes may be applied with greater force for a given manual effort. Y

Being aware of the possibility of modications in the particular structure here-in described without departing from the fundamental principles of my invention, I do not intend that its scope be limited except as set forth by the appended claims.

Having fully described my invention, what I claim as new and desire to secure by Letters' Patent of the United States is:

1. In a fluid pressure system, two fluid actuating motors, a single master cylinder device, conduit means leading to each motor, means for developing hydraulic pressure in the conduit means and motors by operation of the master cylinder, two normally open shut-off valves associated with th`e conduit means each of which is capable of preventing operation of a motor, means for selectively closing the shut-off valves, and means controlled by the movement of a single member y only for operating the last named means :and for operatingthe master cylinder device after a selected shut-off valve is closed or for operating the ,master cylinder device without closing either shut-off valve.

2. In a fluid pressure system, two fluid actuating motors, a master cylinder device, conduit means leading to each motor, means for developing `hydraulicpressure in the conduit means and motors by operation of the master cylinder, two shut-off valves associated with the conduit means each of which is capable of preventing operation of a motor, means comprising. a lever for selectively closing the shut-oir valves, means operable by the lever after a valve is closed for operating the master cylinder device, and means including a fulcrum about which said lever pivots to operate the master cylinder device without closing either shut-off valve.

3. In a fluid pressure system, two fluid actuating motors, a single master cylinder device, conduit means leading to each motor, means for developing hydraulic pressure in the conduit means and motors by operation of the master cylinder, two normally open shut-olf valves associated with the conduit means each of which is capable of preventing operation of a motor, means for selectively closing the shut-off valves and comprising rotatable cam means and a lever movable in one direction from a predetermined position for closing one valve and in another direction from the predetermined position for closing the other valve, and means controlled by a continued movement of said lever in the same diposition for closing one valve and in another direction from the predetermined position for closing the other valve, means controlled by continued movement of said lever for operating the master cylinder device after either valve is closed, means for returning said lever to its normally inoperative position when released, and fulcrum means about which said lever is rockable to enable said lever when said. valves are closed -to operate other valve means to simultaneously operate each of said motors.

5. In a `uid pressure system, three fluid actuating motors, a master cylinder device, conduit means leading to each motor, means for developing hydraulic pressure in the conduit means and motors by operation of the master cylinder, three shut-01T valves-associated with the conduit means each of which is capable of preventing operation of a motor, means comprising a lever for so controlling the closing of the shut-oir valves that one valve together with either one ofthe other two valves can be selectively placed in vclosed position, and means operable by the lever'after it has closed two of the valves for operating the master cylinder device.

6. In a fluid pressure system, three iiuid actuating motors, a master cylinder device, conduit means leading to each motor, means for developing hydraulic pressure in the conduitl means and motors by operation of the master cylinder, three shut-01T valves associated with the conduit means each of which is capable of preventing operation of a motor, means comprising a lever for so controlling the closing of the shut-off valves that one valve together with either one of the other two valves can be selectively placed in closed position, means operable by the` lever after it has closed two of the valves for operating the master cylinder device, and means including a fulcrum about which said lever rocks to operate the master cylinder device without closing any shut-ofiv valve.

7. In a uid pressure actuating system, three uid actuating motors, a hydraulic pressure developing means, conduit means leading to each motor, three normally open shut-oirl valves associated with the conduit means each of which is capable of preventing operation of a motor, means for developing hydraulic pressure in the conduit means and motors by operation of the pressure developing means, means comprising a single manually operable member for so controlling the closing of the shut-01T valves that one valve together with either one of the other two valves can be selectively placed in` closed position, means comprising a master cylinder device for causing hydraulic pressure to be developed in the conduit means leading to each motor, a valveA for preventing communication from the master cylinder to the hydraulic pressure developing means, and means for closing the last named valve and operating the master cylinder by the single manually operable member.

#-8. In a fluid pressure actuating system, three iiuid actuating motors, a master cylinder device,

conduit means leading to each motor. three normally open shut-olf valves associated with the conduit means each of which is capable of preventing operation of a motor, means for developing hydraulic pressure in the conduit means and motors by operation of the master cylinder device, means comprising a single manually oper.. able member for so controlling the closing of the shut-olf valves that one valve together with either one of the other two valves can, be selectively placed in closed position, means comprising a second master cylinder device for causing hydraulic pressure to be developed in the conduit means leading to each motor, and means for operating the second master cylinder device by the single manually operable means after it has closed Y two valves controlled thereby. f

9. In a nuid pressure actuating system, two fluid actuating motors, a master cylinder device, conduit means leading to each motor, two normally open shut-off valves associated with the conduit means each of which is capable of preventing operation of a motor, means for developing hydraulic pressure in the conduit means and motors by operation of the master cylinder device, means comprising a lever for selectively closing the shut-off valves, means comprising a second master cylinder device for causing hydraulic pressure to be developed in the conduit means leading to each motor, a valve for preventing communication from the master cylinder to the hydraulic pressure developing means, and

means for closing the last named valve and operating the second master cylinder by the lever so that a selected motor can be actuated by said second master cylinder independently of operation of the first master cylinder. r

10. In a fluid pressure actuating system, two fluid actuating motors, a master' cylinder device, conduit means leading to each motor, two normally open shut-off valves associated with the conduit means each of which is capable of preventing operation of a motor, means for developing hydraulic pressure in the conduit means and vmotors by operation of the master cylinder device, means comprising a, lever for selectively closing the shut-off valves, means comprisinga second master cylinder device for causing hydraulic pressure to be developed in the conduit means leading to each motor', a normally un' seated check valve for preventing communication from the master cylinder to the hydraulic pressure developing means, means for closing the check valve and operating the second master cylinder by the lever so that a selected motor can beactuated by said second master cylinder independently of operation of the first master cylinder, and means for holding the lever in a position where the check valve is maintained seated.

11. In a fluid pressure actuating system, two fluid actuating motors, a master cylinder device, conduit means leading to each motor, two normally open shut-oft valves associated with the conduit means each of which is capable of preventing operation of a motor, means for develop ing hydraulic pressure in the conduit means and motors by operation of the master cylinder device, means comprising a manually operable lever for selectively closing the shut-oir valves, means comprising a second master cylinder device forA causing hydraulic pressure to be developed in theY by the lever without closing a shut-off valve'.

12. In a fluid pressure system for a vehicle having driving members for each side thereof, brakes for the members, fluid motors for the brakes, a master cylinder device, con-duit means connected to each motor, means for transmitting hydraulic pressure through the conduit means when the master cylinder is operated, two normally open shut-off valves for the conduit means each of which selectively operatesone of said motors, means comprising a member movable in opposite directions from a central position for selectively closing the shut-off valves, means for operating the master cylinder by said member when continued to be moved beyond'the position where a shut-off valve is closed, and fulcrum means about which saidlever is rockable to enable said lever when said valves are closed to operate other valve means to simultaneously operate each of said motors.

13. In a fluid pressure system for a vehicle having driving members for each side thereof, brakes for the members, fluid motors for the brakes, a master cylinder device, conduit means connected to each motor, means for transmitting hydraulic pressure through the conduit means when the master cylinder is operated, two normally open shut-off valves for the conduit means'each of which when closed is capable of preventing operation of a motor, means comprising a member movable in opposite directions from a central position for selectively closing the shut-01T valves, and means for operating the master cylinder by said member when continued to be moved beyond the position'where a, shutoi valve is closed for operating only the master cylinder device by said member when moved in another direction.

14. In a fluid pressure system for a vehicle having driving members for each side thereof, brakes for the members fluid motors for the brakes, a `master cylinder device, conduit means connected to each motor, means for transmitting hydraulic pressure through the conduit means when the master'cylinder is operated, two shutoif valves for the'conduit means each of which is capable of preventing operation of a motor, cam means movable in opposite directions from a central position for selectively closing the `shut-off valves, a rotatable member connected to the cam means and mounted for axial movement, means for moving said member axially when it is 1'0- tatcd to rotate the cam means in said opposite directions, means for rotating said member, and means for operating the master cylinder device by the axial movement of the member,

15. In a fluid pressure system for a vehicle having driving members for each side thereof, brakes for the members, fiuid motors for the brakes, a master cylinder device, conduit means connected to each motor, means for transmitting hydraulic pressure through the conduit means when the master cylinder is operated, two shutoff valves for the conduit means each of which is capable of preventing operation of a motor, cam means movable in opposite directions from a central position for selectively closing the shutofi valves, a rotatable member connected to the cam means and mounted for axial movement relative to the cam means, means for moving said member axially when it is rotated to rotate the cam means in said opposite directions, a lever pivotally connected to the member for rotating said member cr for moving it axially Without' rotation thereof, and means for operating the master cylinder device by the axial movement of the member.

16. In a fluid pressure brake actuating system for a vehicle having a driving member for each side thereof and a dirigible wheel, brakes for the hmembers and wheel, a ud motor for each brake,

a source of developed hydraulic pressure, conduit means leading to each motor, means operable by developed hydraulic pressure for forcing liquid under pressure through the conduit means to each motor, normally open shut-of! valves associated with the conduit means each of which is capable lof preventing operation of a motor, means for controlling the closing of said valves so that the motors of the brakes on the driving members only may be selectively operated, means comprising a single master cylinder device connected to also cause liquid under pressure to be forced through the conduit means to the motors independently of fluid pressure from said source. and means including a common operated member for `operating the means for controlling the closing of the shutoff valves in a selective manner and subsequently operating the master cylinder to produce presy sure.

trolling the closing of said-valves so that the motors of the brakes on the' driving members only may be selectively operated, means comprising a master cylinder device connected to also cause liquid under pressure to be forced through the conduit means to the motors, means including a common operated member for operating the means for controlling the closing of the shut-off valves in a selective manner and subsequently operating the master cylinder or for operating the master cylinder device independently of the closing of -any shut-off valve to cause operation of all the motors.

18. In a fluid pressure brake actuating system for a vehicle having a driving member for each side thereof and a dirigible wheel, brakes for the members and wheel, means for actuating all the brakes including a force developing device, means associated with the actuating means for selectively permitting the actuation of the brakes of the driving members only, a single member for controlling said last named means, and means operable by the single member after it has been operated to select a driving member brake and by Y a continued movement thereof for actuating said selected brake independently of operation of the force developing device.

19. In afluid pressure system for a vehicle having driving members for each side thereof, brakes for the members, fluid motors for the brakes, two hydraulic pressure developing means each of which is connected to actuate the brakes, means for selectively' causing one brake only to be actuated, a movable member .for controlling said selection, and means operable by continued movement of said member after a selection by predetermined movements thereof is made to cause operation, .of one of the hydraulic pressure producing means to produce pressure so'that the brake on either selected driving member can be actuated independently of the operation of the other hydraulic pressure producing means.

20. In. a uid pressure system for a vehicle having a driving member for each side thereof brakes for the members. uid motors for the brakes, a master cylinder, conduit means between the master cylinder and each motor, shutoiT valves for the conduit means each of which is capable ofpreventing operation of a motor, a power cylinder for operating the master cylinder.

a source oiV fluid pressure dmerent from atmospheric pressure connected to operate the power cylinder, a control valve for the source. means comprising two other master cylinders each of which is capable of controlling the control valve, and means comprising a single control member for selectively closing a shut-oi! valve and then subsequently operating one of the last two named mastercylinders to cause the power cylinder to 10 operate the rst named master cylinder.

WERNER. F. BOLDT. 

